The measurement ofthe human body's thermal radiation at microwave frequencies can reveal temperature anomalies at depths of several centimeters in the body. We have developed two microwave radiometers at frequencies of 3.3 and 1.3 GHz (wavelengths of 9.1 and 23 cm respectively) for this specific application and will apply these in clinical tests on patients suspected of having breast tumors, cerebrovascula blockage, and other applictions suggested to us by physicians. The method is passive, non-invasive, and the patient is not subjected to any external radiation. Preliminary statistics, based on 23 breast cancer cses and over 600 normals, indcate detection rates comparable with infrared thermography and xero-mammography. We plan to construct a 6 GHz radiometer, with integral microprocessor for data acquisition and analysis, in order to optimize our detection statistics. BIBLIOGRAPHIC REFERENCES: Barrett, Alan H., and Myers, Philip C. 1975, "Subcutaneous Temperatures: A Method of Noninvasive Sensing," Science, 190, 669.